You can set the VNH3SP0 to "brake" mode. But this works or not depending on the motor and gearing. It is very easy to test if it will work. Twist the leads of the DC motor together. With shorted leads, the DC motor should resist rotation, to what degree depends on the motor. The other mode is "coast" which is simply an open circuit. Then you have forward and reverse modes as well.
To handle shoot through, just never switch from forward to reverse or vice versa without first going to either "coast" or "brake". Yes, you can look at the datasheet and count microseconds but if the PID runs at 1000 Hz you are guaranteed to always remain in one of those four states for at minimum 1/1000th second. If switching directions "brake" might even help, depends on the motor. As for the design of those internal MOSFETs, just try doing better. They needed to open the lower side of the bridge and there is no negative voltage available and they want low on-resistance. This used to be really hard to do. (But today we have logic-level MOSFETs) On Thu, Oct 29, 2020 at 5:54 AM Gene Heskett <ghesk...@shentel.net> wrote: > On Wednesday 28 October 2020 18:05:06 Gene Heskett wrote: > > Since I have these OLIMEX gismos that are useless at 24 volts, but Chris > claims zero heat at 12 volts, I do have a couple places I can use these. > > I have a tiny peristaltic pump which delivers an invisible mist to cool > the tool and prevent its packing full of alu and snapping it off halfway > thru the job. Using two cross-coupled one shots to generate an on/off > signal for a transistor running the pump. the individual one shots are > controlled by pyvcp sliders so I can independently control the on off > time. These pumps work by rollers on thin walled si tubing and haven't > the best expected lifetime before the si tubing cracks and fails. > Currently the armature is advancing 15 or so degrees, but rebounding > 14.5 degrees, which is subjecting the tubing to a lot of flexing it > doesn't need. > > Since these OLIMEX things can crowbar the motor in the pwm off state, > that should discourage most of the springback, and only require an on > time to move a degree per pulse, much less repeated flexing of the pump > tube should result. So since I do have 12 volts to run it with on the > 6040, that will be my next project. I bought 4 of those pumps knowing > they have a limited lifetime, but if this works on the 6040, I've 2 of > these otherwise useless OLIMEX gismo's, so the 2nd one will either go on > the G0704 or maybe on the Sheldon. The G0704 needs it the worst. > > So there you have it, a potential way to run a mister pump, at flow rates > so dry its not messy but still gets the cooling job done. My present > method works but is much harder on the pumps tubing than it needs to be. > > Cheers, Gene Heskett > -- > "There are four boxes to be used in defense of liberty: > soap, ballot, jury, and ammo. Please use in that order." > -Ed Howdershelt (Author) > If we desire respect for the law, we must first make the law respectable. > - Louis D. Brandeis > Genes Web page <http://geneslinuxbox.net:6309/gene> > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > -- Chris Albertson Redondo Beach, California _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
